The character carefully untangles the magicka woven into a failed enchantment, recovering the lost energy.
When the character fails an Enchant test to create an enchantment they can make another Enchant test at a -40 penalty. On success, the soul gem is not destroyed and maintains all of its soul energy. Alternatively, they may attempt the test at a -20 penalty. On a success the gem survives, but with no energy.